Evolutionary systems and game theory dictates that the things we call rights are necessary.
Any replicating system will get to a point where the parts of the system acknowledge that self-preservation, and things that make self-preservation easier, is the key to happiness. Rights, as a concept, is a trade-of-agreements you make with your fellow man to enhance this preservation.
..."all humans are inherently entitled to life, liberty, and property" doesn't actually mean anything, and another person could just as easily make a contrary claim without any more evidence that it's actually tru
Entitlement to life:
Will we be able to preserve ourselves if there is no agreement against killing each other? We can trash this agreement but we will spend a large percent of our time looking over our shoulder at every step we make. We will lose all the time and mental capacity to do anything that will benefit ourselves, the people we care about, the species, and the system. We will surely lose the time and capability to ponder this question (think Maslow's pyramid).
Entitlement to liberty:
How are we going to preserve ourselves if we don't let each other be? We are all different. The fact is there are various cultures, beliefs, rituals, state-of-minds, histories, and many other things we don't have control over, but here we are. Liberty allows you exercise these personal traits of yours. Liberty is there to relieve you of the preoccupation to conform. For if you are preoccupied with changing your nature, you will spend less time preserving yourself and the rest of the species. It's detrimental to the system.
Entitlement to property:
How are we going to preserve ourselves if we have no where to preserve ourselves and practice our liberty? Would you do anything if the concept of having something didn't exist? What is the point of working and preserving the well-being of the environment you live in (which will in turn lead to self-preservation) if you aren't going to have the ability to call something yours at the end? This is mainly for the evolution of the human system for the better, where better is something that leads to easier self-preservation.
Are these arbitrary? Maybe, but then what isn't? What makes something not arbitrary? Only one thing, a creator where absolute reality stems from. I think almost any complex evolutionary system (biological or not) will, at some point, develop rules and agreements that will preserve the perpetuation of the system. This happens blindly.